//Given a binary search tree (BST), find the lowest common ancestor (LCA) of two
// given nodes in the BST. 
//
// According to the definition of LCA on Wikipedia: “The lowest common ancestor 
//is defined between two nodes p and q as the lowest node in T that has both p and
// q as descendants (where we allow a node to be a descendant of itself).” 
//
// 
// Example 1: 
//
// 
//Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8
//Output: 6
//Explanation: The LCA of nodes 2 and 8 is 6.
// 
//
// Example 2: 
//
// 
//Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4
//Output: 2
//Explanation: The LCA of nodes 2 and 4 is 2, since a node can be a descendant o
//f itself according to the LCA definition.
// 
//
// Example 3: 
//
// 
//Input: root = [2,1], p = 2, q = 1
//Output: 2
// 
//
// 
// Constraints: 
//
// 
// The number of nodes in the tree is in the range [2, 105]. 
// -109 <= Node.val <= 109 
// All Node.val are unique. 
// p != q 
// p and q will exist in the BST. 
// 
// Related Topics 树 
// 👍 530 👎 0


//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        TreeNode ancestor = root;
        while(true){
            if(p.val < ancestor.val && q.val < ancestor.val) {
                ancestor = ancestor.left;
            }else if (p.val > ancestor.val && q.val > ancestor.val) {
                ancestor = ancestor.right;
            }else {
                break;
            }
        }
        return ancestor;
    }
}
//leetcode submit region end(Prohibit modification and deletion)
